Emergency starting compressors are normally driven by a small hand-start diesel engine and they should be of the air-cooled type since, in the ease of a dead ship start up situation, there would be no power available, for cooling water pumps.
The Tanabe "H" series 2 stage, water cooled compressor has proved to be one of the most popular starting compressors ever built. It was developed from the experience, which we gained from its predecessor, the "HC" which was produced in various forms over a period of 20 years.
The basic module is a vertical double acting cylinder with a first stage bore of either 6 or 7 inches diameter. The stroke length can be either 3 or 4 inches. These figures are used to specify the model type, e.g. H-63 or H-74. The optimum capacity for a single cylinder (type H-74) operating at 1,800 rpm is 200 m3/hr.
Duplicating the cylinders, doubles the capacity (type H-274) whilst 3 cylinders (type H-374) gives 600 m3/hr. The beauty of this system is the simplification of parts required. Valves, pistons, rings etc are common parts throughout, even for compressors with differing capacities. In total there are 13 different combinations in the range, giving outputs from 60 to 600 m3/hr.
Control Air Compressors
This type of compressor must also be approved by class and is often (though not always) of the oil-free type. Typical operating pressure would be 7〜9 bar. These oil-free compressors are normally reciprocating type compressors using piston rings made from PTFE (Teflon). The Tanabe design incorporates 2 air cooled cylinders in a 90°vee formation.
General Service Air Compressors
Typical operating pressure would be 7〜10 bar. This compressor does not need a class approval certificate but this does not mean that any industrial compressor can be used for this duty.
Occasionally reciprocating compressors are still used but an oil-injected screw compressor is the most common choice. These usually consist of a self-contained unit, with the compressor, motor and electric control panel encapsulated in an acoustic capsule. Cooling can be by either air or water.
